1. AN ORGANISATION FOR A NATIONAL EARTH SCIENCE INFRASTRUCTURE PROGRAM Ben Caradoc-Davies CSIRO Earth Science and Resource Engineering Free and Open Source Software for Geospatial Sydney, Australia, 20-23 October 2009 GeoServer application schema support: complex features for the masses

2. GeoServer Java servlet for OGC Web Services WMS, WFS, WFS-T,... Open Source (GPL) Built on GeoTools (LGPL) Reference OGC Web Feature Service implementation Originally supported only simple features app-schema adds complex feature WFS (only)

3. Simple Feature Flat XML representation of one database table

4. Simple Feature Type autogenerated by GeoServer All properties in one namespace Database schema exposed to consumer Meaning implied by element names Semantics often have to be inferred by user 209589 urn:cgi:feature:PIRSA:MappedFeature:209589 SEE PLAN 68-611 (DISUSED) Map Plot urn:cgi:classifierScheme:PIRSA:ObservationMethod urn:cgi:feature:PIRSA:MineralOccurrence:43deposit -26.8760644 133.0181594 urn:ogc:def:nil:OGC::missing http://urn.opengis.net/

5. Complex Feature Nested XML representation of multiple related database tables

6. Complex Feature Represents object relationships Types defined in GML application schema Meaning specified in community-agreed information standard SEE PLAN 68-611 urn:cgi:feature:PIRSA:MappedFeature:209589 (DISUSED) Map Plot urn:ogc:def:nil:OGC::missing 133.0181594 -26.8760644

7. Why Complex Features? Simple features: Represent database table as XML Interoperability through simplicity Complex features: GML application schema defines complex types Represent object relationships Polymorphism, aggregation, inheritance Extensible information model Scales to large problems and communities

8. GML Application Schema Examples GeoSciML: a GML application schema for the exchange of geoscience data http://www.geosciml.org/ EarthResourceML extends GeoSciML http://www.earthresourceml.org/ Observations and Measurements SensorML CityML

9. Example: AuScope Discovery Portal Three Australian jurisdictions: Victoria (GSV) – deegree Tasmania (MRT) – GeoServer app-schema South Australia (PIRSA) – GeoServer app-schema (hosted by CSIRO) EarthResourceML (derived from GeoSciML) Interoperability through complex feature types defined in a GML application schema Community-agreed information standard

10. http://portal.auscope.org/

11. History of GeoServer app-schema 2005-2007: GeoServer community-schemas Rob Atkinson, Gabriel Roldán Geochemistry roadshow (CSIRO) Fork of a branch (not dead, just sleeping) Informed GeoAPI and GeoTools development 2008: ported to trunk by AuScope Renamed Geoserver app-schema Now: plugin for GeoServer 2.0-beta2 and later

12. How app-schema works Built on GeoTools data stores Maps simple features into complex features Works both ways, so supports queries

13. Installation and Configuration app-schema plugin for vanilla GeoServer Can coexist with simple feature types Configure by hand-editing XML mapping files Driven by GML application schema Define schema URL in mapping file Feature chaining: Define feature types separately and use as properties of each other

14. Mapping File Defines mappings: From: column in database To: XPath in encoded XML Use CQL expressions Set XML attributes gsml:observationMethod/gsml:CGI_TermValue/gsml:value OBSERVATION_METHOD codeSpace OBSERVATION_METHOD_CODESPACE

15. Feature Chaining Define feature types separately Use features as properties of each other Simplifies configuration Equivalent to a foreign key reference gsml:occurrence OCCURRENCE_URN gsml:MappedFeature gml:name

16. Strengths No XSLT programming Configurable through straightforward mapping Uses existing GeoTools/GeoServer components JDBC data sources: PostGIS, Oracle, ArcSDE Shapefiles, property files Good performance Strong developer community and user base Aids adoption of GML application schemas

17. Weaknesses No XSLT programming No data-driven polymorphism Type of each property fixed at mapping time No configuration web interface Hand-edit XML files Tedious and error-prone Requires knowledge of application schema Requires understanding of GML encoding rules

18. Future Work Support for data-driven polymorphism Configuration web interface Aid navigation of GML application schema

19. Conclusion Complex feature types: Defined in a GML application schema Represent object relationships Extensible information model Community-agreed information standard GeoServer app-schema plugin: Reuses existing community-supported components Configured with XML mapping files Maps simple features into complex features

20. Resources GeoServer User Manual: Application Schema Support http://docs.geoserver.org/trunk/en/user/data/app-schema/ Application Schema Support: Tutorial http://docs.geoserver.org/trunk/en/user/data/app-schema/tutorial.html GeoServer app-schema development https://www.seegrid.csiro.au/twiki/bin/view/Infosrvices/GeoserverDevelopment PIRSA EarthResource GeoServer https://twiki.auscope.org/twiki/bin/view/Grid/PirsaEarthResourceGeoserver AuScope Discovery Portal http://portal.auscope.org/

21. Credits Rini Angreani, co-maintainer of app-schema and author of app-schema feature chaining. Rob Atkinson, Gabriel Roldán, Jody Garnett, Justin Deoliveira, and the rest of the GeoTools and GeoServer communities. Simon Cox, and the rest of the GeoSciML community. CSIRO is Australia's national science agency. AuScope Ltd is funded under the National Collaborative Research Infrastructure Strategy (NCRIS), an Australian Commonwealth Government Programme.